/*
 * Copyright 2008 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;
using System.Collections.Generic;
using System.Text;
using ZXing.Common;

namespace ZXing.OneD
{
   /// <summary>
   ///   <p>Decodes Code 39 barcodes. This does not support "Full ASCII Code 39" yet.</p>
   /// 	<author>Sean Owen</author>
   /// @see Code93Reader
   /// </summary>
   public sealed class Code39Reader : OneDReader
   {
      internal static String ALPHABET_STRING = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. *$/+%";
      private static readonly char[] ALPHABET = ALPHABET_STRING.ToCharArray();

      /// <summary>
      /// Returns a string with all possible characters
      /// </summary>
      public static string Alphabet
      {
         get { return ALPHABET_STRING; }
      }

      /// <summary>
      /// These represent the encodings of characters, as patterns of wide and narrow bars.
      /// The 9 least-significant bits of each int correspond to the pattern of wide and narrow,
      /// with 1s representing "wide" and 0s representing narrow.
      /// </summary>
      internal static int[] CHARACTER_ENCODINGS = {
                                                    0x034, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064, // 0-9
                                                    0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00D, 0x10C, 0x04C, 0x01C, // A-J
                                                    0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016, // K-T
                                                    0x181, 0x0C1, 0x1C0, 0x091, 0x190, 0x0D0, 0x085, 0x184, 0x0C4, 0x094, // U-*
                                                    0x0A8, 0x0A2, 0x08A, 0x02A // $-%
                                                 };

      private static readonly int ASTERISK_ENCODING = CHARACTER_ENCODINGS[39];

      private readonly bool usingCheckDigit;
      private readonly bool extendedMode;
      private readonly StringBuilder decodeRowResult;
      private readonly int[] counters;

      /// <summary>
      /// Creates a reader that assumes all encoded data is data, and does not treat the final
      /// character as a check digit. It will not decoded "extended Code 39" sequences.
      /// </summary>
      public Code39Reader()
         :this(false)
      {
      }

      /// <summary>
      /// Creates a reader that can be configured to check the last character as a check digit.
      /// It will not decoded "extended Code 39" sequences.
      /// </summary>
      /// <param name="usingCheckDigit">if true, treat the last data character as a check digit, not
      /// data, and verify that the checksum passes.</param>
      public Code39Reader(bool usingCheckDigit)
         :this(usingCheckDigit, false)
      {
      }

      /// <summary>
      /// Creates a reader that can be configured to check the last character as a check digit,
      /// or optionally attempt to decode "extended Code 39" sequences that are used to encode
      /// the full ASCII character set.
      /// </summary>
      /// <param name="usingCheckDigit">if true, treat the last data character as a check digit, not
      /// data, and verify that the checksum passes.</param>
      /// <param name="extendedMode">if true, will attempt to decode extended Code 39 sequences in the text.</param>
      public Code39Reader(bool usingCheckDigit, bool extendedMode)
      {
         this.usingCheckDigit = usingCheckDigit;
         this.extendedMode = extendedMode;
         decodeRowResult = new StringBuilder(20);
         counters = new int[9];
      }

      /// <summary>
      ///   <p>Attempts to decode a one-dimensional barcode format given a single row of
      /// an image.</p>
      /// </summary>
      /// <param name="rowNumber">row number from top of the row</param>
      /// <param name="row">the black/white pixel data of the row</param>
      /// <param name="hints">decode hints</param>
      /// <returns><see cref="Result"/>containing encoded string and start/end of barcode</returns>
      override public Result decodeRow(int rowNumber, BitArray row, IDictionary<DecodeHintType, object> hints)
      {
         for (var index = 0; index < counters.Length; index++)
            counters[index] = 0;
         decodeRowResult.Length = 0;

         int[] start = findAsteriskPattern(row, counters);
         if (start == null)
            return null;

         // Read off white space    
         int nextStart = row.getNextSet(start[1]);
         int end = row.Size;

         char decodedChar;
         int lastStart;
         do
         {
            if (!recordPattern(row, nextStart, counters))
               return null;

            int pattern = toNarrowWidePattern(counters);
            if (pattern < 0)
            {
               return null;
            }
            if (!patternToChar(pattern, out decodedChar))
               return null;
            decodeRowResult.Append(decodedChar);
            lastStart = nextStart;
            foreach (int counter in counters)
            {
               nextStart += counter;
            }
            // Read off white space
            nextStart = row.getNextSet(nextStart);
         } while (decodedChar != '*');
         decodeRowResult.Length = decodeRowResult.Length - 1; // remove asterisk

         // Look for whitespace after pattern:
         int lastPatternSize = 0;
         foreach (int counter in counters)
         {
            lastPatternSize += counter;
         }
         int whiteSpaceAfterEnd = nextStart - lastStart - lastPatternSize;
         // If 50% of last pattern size, following last pattern, is not whitespace, fail
         // (but if it's whitespace to the very end of the image, that's OK)
         if (nextStart != end && (whiteSpaceAfterEnd << 1) < lastPatternSize)
         {
            return null;
         }

         // overriding constructor value is possible
         bool useCode39CheckDigit = usingCheckDigit;
         if (hints != null && hints.ContainsKey(DecodeHintType.ASSUME_CODE_39_CHECK_DIGIT))
         {
            useCode39CheckDigit = (bool) hints[DecodeHintType.ASSUME_CODE_39_CHECK_DIGIT];
         }

         if (useCode39CheckDigit)
         {
            int max = decodeRowResult.Length - 1;
            int total = 0;
            for (int i = 0; i < max; i++)
            {
               total += ALPHABET_STRING.IndexOf(decodeRowResult[i]);
            }
            if (decodeRowResult[max] != ALPHABET[total % 43])
            {
               return null;
            }
            decodeRowResult.Length = max;
         }

         if (decodeRowResult.Length == 0)
         {
            // false positive
            return null;
         }

         // overriding constructor value is possible
         bool useCode39ExtendedMode = extendedMode;
         if (hints != null && hints.ContainsKey(DecodeHintType.USE_CODE_39_EXTENDED_MODE))
         {
            useCode39ExtendedMode = (bool)hints[DecodeHintType.USE_CODE_39_EXTENDED_MODE];
         }

         String resultString;
         if (useCode39ExtendedMode)
         {
            resultString = decodeExtended(decodeRowResult.ToString());
            if (resultString == null)
            {
               if (hints != null && 
                   hints.ContainsKey(DecodeHintType.RELAXED_CODE_39_EXTENDED_MODE) &&
                   Convert.ToBoolean(hints[DecodeHintType.RELAXED_CODE_39_EXTENDED_MODE]))
                  resultString = decodeRowResult.ToString();
               else
                  return null;
            }
         }
         else
         {
            resultString = decodeRowResult.ToString();
         }

         float left = (start[1] + start[0])/2.0f;
         float right = lastStart + lastPatternSize / 2.0f;

         var resultPointCallback = hints == null || !hints.ContainsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK)
                                      ? null
                                      : (ResultPointCallback) hints[DecodeHintType.NEED_RESULT_POINT_CALLBACK];
         if (resultPointCallback != null)
         {
            resultPointCallback(new ResultPoint(left, rowNumber));
            resultPointCallback(new ResultPoint(right, rowNumber));
         }

         return new Result(
            resultString,
            null,
            new[]
               {
                  new ResultPoint(left, rowNumber),
                  new ResultPoint(right, rowNumber)
               },
            BarcodeFormat.CODE_39);
      }

      private static int[] findAsteriskPattern(BitArray row, int[] counters)
      {
         int width = row.Size;
         int rowOffset = row.getNextSet(0);

         int counterPosition = 0;
         int patternStart = rowOffset;
         bool isWhite = false;
         int patternLength = counters.Length;

         for (int i = rowOffset; i < width; i++)
         {
            if (row[i] ^ isWhite)
            {
               counters[counterPosition]++;
            }
            else
            {
               if (counterPosition == patternLength - 1)
               {
                  if (toNarrowWidePattern(counters) == ASTERISK_ENCODING)
                  {
                     // Look for whitespace before start pattern, >= 50% of width of start pattern
                     if (row.isRange(Math.Max(0, patternStart - ((i - patternStart) >> 1)), patternStart, false))
                     {
                        return new int[] { patternStart, i };
                     }
                  }
                  patternStart += counters[0] + counters[1];
                  Array.Copy(counters, 2, counters, 0, patternLength - 2);
                  counters[patternLength - 2] = 0;
                  counters[patternLength - 1] = 0;
                  counterPosition--;
               }
               else
               {
                  counterPosition++;
               }
               counters[counterPosition] = 1;
               isWhite = !isWhite;
            }
         }
         return null;
      }

      // For efficiency, returns -1 on failure. Not throwing here saved as many as 700 exceptions
      // per image when using some of our blackbox images.
      private static int toNarrowWidePattern(int[] counters)
      {
         int numCounters = counters.Length;
         int maxNarrowCounter = 0;
         int wideCounters;
         do
         {
            int minCounter = Int32.MaxValue;
            foreach (var counter in counters)
            {
               if (counter < minCounter && counter > maxNarrowCounter)
               {
                  minCounter = counter;
               }
            }
            maxNarrowCounter = minCounter;
            wideCounters = 0;
            int totalWideCountersWidth = 0;
            int pattern = 0;
            for (int i = 0; i < numCounters; i++)
            {
               int counter = counters[i];
               if (counter > maxNarrowCounter)
               {
                  pattern |= 1 << (numCounters - 1 - i);
                  wideCounters++;
                  totalWideCountersWidth += counter;
               }
            }
            if (wideCounters == 3)
            {
               // Found 3 wide counters, but are they close enough in width?
               // We can perform a cheap, conservative check to see if any individual
               // counter is more than 1.5 times the average:
               for (int i = 0; i < numCounters && wideCounters > 0; i++)
               {
                  int counter = counters[i];
                  if (counter > maxNarrowCounter)
                  {
                     wideCounters--;
                     // totalWideCountersWidth = 3 * average, so this checks if counter >= 3/2 * average
                     if ((counter << 1) >= totalWideCountersWidth)
                     {
                        return -1;
                     }
                  }
               }
               return pattern;
            }
         } while (wideCounters > 3);
         return -1;
      }

      private static bool patternToChar(int pattern, out char c)
      {
         for (int i = 0; i < CHARACTER_ENCODINGS.Length; i++)
         {
            if (CHARACTER_ENCODINGS[i] == pattern)
            {
               c = ALPHABET[i];
               return true;
            }
         }
         c = '*';
         return false;
      }

      private static String decodeExtended(String encoded)
      {
         int length = encoded.Length;
         StringBuilder decoded = new StringBuilder(length);
         for (int i = 0; i < length; i++)
         {
            char c = encoded[i];
            if (c == '+' || c == '$' || c == '%' || c == '/')
            {
               if (i + 1 >= encoded.Length)
               {
                  return null;
               }

               char next = encoded[i + 1];
               char decodedChar = '\0';
               switch (c)
               {
                  case '+':
                     // +A to +Z map to a to z
                     if (next >= 'A' && next <= 'Z')
                     {
                        decodedChar = (char)(next + 32);
                     }
                     else
                     {
                        return null;
                     }
                     break;
                  case '$':
                     // $A to $Z map to control codes SH to SB
                     if (next >= 'A' && next <= 'Z')
                     {
                        decodedChar = (char)(next - 64);
                     }
                     else
                     {
                        return null;
                     }
                     break;
                  case '%':
                     // %A to %E map to control codes ESC to US
                     if (next >= 'A' && next <= 'E')
                     {
                        decodedChar = (char)(next - 38);
                     }
                     else if (next >= 'F' && next <= 'W')
                     {
                        decodedChar = (char)(next - 11);
                     }
                     else
                     {
                        return null;
                     }
                     break;
                  case '/':
                     // /A to /O map to ! to , and /Z maps to :
                     if (next >= 'A' && next <= 'O')
                     {
                        decodedChar = (char)(next - 32);
                     }
                     else if (next == 'Z')
                     {
                        decodedChar = ':';
                     }
                     else
                     {
                        return null;
                     }
                     break;
               }
               decoded.Append(decodedChar);
               // bump up i again since we read two characters
               i++;
            }
            else
            {
               decoded.Append(c);
            }
         }
         return decoded.ToString();
      }
   }
}